Optoelectronic semiconductor device and light signal input/output device

ABSTRACT

A optoelectronic semiconductor device, mountable on and electrically connectable to an electro-optical wiring board, a substrate thereof having a light input/output through-hole and electric connection through-holes, the light input/output through-hole being not formed in a stressed area of the circuit wiring board, but formed in a non-stressed area of the circuit wiring board, the stressed area being an area where a stress is larger in value than the mean value of stresses caused in the circuit wiring board by a difference in coefficient of thermal expansion between the circuit wiring board and the electro-optical wiring board when the electrode on the semiconductor optoelectronic device is mechanically fixed to and electrically connected to the electro-optical wiring board.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2003-308917, filed on Sep. 1,2003, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optoelectronic semiconductor deviceand a light signal input/output device.

2. Background Art

In recent years, optical interconnection technology has been seen as aleading technology for long-distance, large-capacity signaltransmission. Optical interconnection technology uses light to transmitsignals within an electronic device of a system and between electronicdevices. For example, an optical subscriber line in an FTTH (Fiber ToThe Home) system is one kind of optical interconnection technology in abroad sense, as an optical fiber is used to transmit information from acenter station to each subscriber.

Electrical signal transmission is known as one way of transmittingsignals at a high speed. In order to improve the performance ofelectronic signal transmission modules, much research and developmenthas been conducted on improving the performance of silicon LSIs. As aresult, the operation speed and the integration scale of LSIs have beenimproved remarkably. However, with respect to the improvement of theperformance of electronic signal transmission modules, there are stillproblems to be solved, i.e., the improvement of the transmission rateand the wiring density of electrical signal lines. Specifically, even ifthe performance of transistors and other functional elements in an LSIis improved, a lack of improvement of the transmission rate and thewiring density of electrical signal lines would serve as a rate limitingfactor, and prevent the improvement in performance of electronic signaltransmission modules. Furthermore, signal transmission delays inelectrical signal transmission lines also serve as a limiting factor forthe improvement in performance of electronic signal transmissionmodules. Even if a higher signal transmission rate and a higher wiringdensity of electrical boards can be achieved, the influence of EMI(Electromagnetic Interference) is still notable. For the aforementionedreasons, optical interconnection technology has been attractingattention as a technology for solving the above problems of theelectronic signal transmission modules.

In optical interconnection technology, a light signal input/outputdevice receives a light signal, performs a redetermined processingoperation on the light signal, and then retransmits the processed lightsignal. In the light signal input/output device, an optoelectronicsemiconductor device is provided on an electro-optical wiring boardhaving electric wires and optical waveguides formed therein. Theoptoelectronic semiconductor device includes a photoreceptor orphotodetector element, which receives a light signal from the opticalwaveguides and converts the light signal into an electronic signal; asemiconductor integrated circuit element, which processes the electronicsignal from the photoreceptor; and a light emitting element, whichconverts the electronic signal from the semiconductor integrated circuitelement into a light signal and retransmits the light signal to theoptical waveguide. The light signal input/output device is disclosed in,for example, Japanese Patent Publication No. 2000-332301.

Optoelectronic semiconductor devices are becoming smaller and denser,and optoelectronic semiconductor devices of about 10 mm×10 mm in sizeare common. In order to effectively perform the miniaturization and theincrease in density, the BGA (Ball Grid Array) mounting technique isseen as an effective technique for mounting an optoelectronicsemiconductor device on an electro-optical wiring board. A BGA has astructure in which solder ball electrodes are arranged to form a grid.The BGA structure is smaller than that of a QFP (Quad Flat Package)using outer-lead electrode terminals since the solder ball electrodesoccupy less space. Furthermore, the BGA structure incurs no suchdeformation of lead as will occur frequently with the QFP. Moreover, thesurface tension of the solder balls being molten causes a self-alignmenteffect which automatically corrects a misalignment having occurredduring the mounting of the optoelectronic semiconductor device. Anoptoelectronic semiconductor device employing the BGA structure isdisclosed in Japanese Patent Publication No. 2001-185752, for example.

As optical interconnection technology is likely to become a higherdensity and higher speed communication technology for the nextgeneration, it is essential to ensure a highly reliable connectionbetween the optoelectronic semiconductor device and the electro-opticalwiring board, and to accurately position them in relation to each other.For achieving such connection and positioning, the above-mentioned BGAmounting technique is particularly promising.

In a conventional optoelectronic semiconductor device using the BGAmounting technique, a cavity is formed in the lower of upper and lowersides of a circuit wiring board where solder ball electrodes are formed,and an optoelectronic semiconductor element and a semiconductorintegrated circuit element are placed in the cavity so that theoptoelectronic semiconductor element and the electro-optical wring boardmay face each other, as disclosed in Japanese Patent Publication No.2001-185752. This method (cavity-down BGA) is effective for theimprovement of the heat radiation characteristic as well as forminiaturizing the device. However, since the manufacturing cost of thecircuit wiring board having the cavity is high, the packaging cost ofthe semiconductor device is also high.

There are optoelectronic semiconductor devices in which majorconsideration is given to a decrease in the manufacturing cost. In sucha case, circuit elements can be provided on the upper side of a circuitwiring board while solder ball electrodes can be provided on the lowerside of the circuit wiring board. In such an optoelectronicsemiconductor device, it is necessary to form light input/outputthrough-holes in the circuit wiring board in order to transfer a lightsignal between an optoelectronic semiconductor element and anelectro-optical wiring board. However, it is considered extremelydifficult to actually use this technique. That is, in opticalinterconnection technology, high density transmission is performed withan increased number of light signals. Accordingly, an increased numberof light signals are used in the optoelectronic semiconductor device.Thus, the optoelectronic semiconductor device has many optoelectronicsemiconductor elements provided therein. When circuit elements areprovided on the upper side of the circuit wiring board, however, sincethey are disposed in the form of a one-dimensional array on theperiphery of a semiconductor integrated circuit element, the size of thecircuit wiring board increases. When the circuit wiring board becomeslarger, a stress-induced strain caused by the difference in thecoefficient of thermal expansion (CTE) between the circuit wiring boardand the electro-optical wiring board also becomes larger. In addition,since the light input/output through-holes are formed in the circuitwiring board as described above, the strength of the circuit wiringboard is decreased. Therefore, it has been believed that if the circuitelements are provided on the upper side of the circuit wiring board, astress-induced strain would cause damage to the circuit wiring board,and/or would peel off the solder ball electrodes, thereby decreasing thereliability of the device.

BRIEF SUMMARY OF THE INVENTION

An optoelectronic semiconductor device, mountable on and electricallyconnectable to an electro-optical wiring board, according to a firstaspect of the present invention includes:

-   -   an optoelectronic semiconductor element to receive a light        signal, transmit a light signal or transmit and receive a light        signal;    -   a semiconductor integrated circuit element electrically        connected to the optoelectronic semiconductor element; and    -   a circuit wiring board comprising:        -   a substrate having:            -   first and second sides opposite to each other in the                direction of the thickness, the optoelectronic                semiconductor element and the semiconductor integrated                circuit element being mounted on the first side;            -   a light input/output through-hole, the optoelectronic                semiconductor element inputting/outputting a light                signal via the light input/output through-hole; and            -   an electric connection through-hole, the semiconductor                integrated circuit element inputting/outputting an                electric signal via wiring layers filled in the electric                connection through-holes; and        -   an electrode formed on the second side of the substrate,            connected to the wiring layers filled in the electric            connection through-holes, and mountable on and electrically            connectable to the electro-optical wiring board,            the light input/output through-hole being not formed in a            stressed area of the circuit wiring board, but formed in a            non-stressed area of the circuit wiring board, the stressed            area being an area where a stress is larger in value than            the mean value of stresses caused in the circuit wiring            board by a difference in coefficient of thermal expansion            between the circuit wiring board and the electro-optical            wiring board when the electrodes on the optoelectronic            semiconductor device are mechanically fixed to and            electrically connected to the electro-optical wiring board.

A light signal input/output device according to a second aspect of thepresent invention includes:

-   -   an electro-optical wiring board; and    -   semiconductor devices mounted on the electro-optical wiring        device,    -   one of the semiconductor devices being an optoelectronic        semiconductor device which comprises:    -   an optoelectronic semiconductor element to receive a light        signal, transmit a light signal or transmit and receive a light        signal;    -   a semiconductor integrated circuit electrically connected to the        optoelectronic semiconductor element; and    -   a circuit wiring board comprising:        -   a substrate having:            -   first and second sides opposite to each other in the                direction of the thickness, the optoelectronic                semiconductor element and the semiconductor integrated                circuit element being mounted on the first side;            -   a light input/output through-hole, the optoelectronic                semiconductor element inputting/outputting a light                signal via the light input/output through-hole; and            -   an electric connection through-holes, the semiconductor                integrated circuit element inputting/outputting a                electric signal via wiring layers filled in the electric                connection through-holes; and            -   an electrode formed on the second side of the substrate,                connected to the wiring layers filled in the electric                connection through-holes, and mountable on and                electrically connectable to the electro-optical wiring                board, the light input/output through-hole being not                formed in a stressed area of the circuit wiring board,                but formed in a non-stressed area of the circuit wiring                board, the stressed area being an area where a stress is                larger in value than the mean value of stresses caused                in the circuit wiring board by a difference in the                coefficient of thermal expansion between the circuit                wiring board and the electro-optical wiring board when                the electrode on the optoelectronic semiconductor device                is mechanically fixed to and electrically connected to                the electro-optical wiring board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an optoelectronic semiconductordevice according to an embodiment of the present invention.

FIG. 2 is a plane-sectional view of the optoelectronic semiconductordevice according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a light signal input/output deviceaccording to the embodiment of the present invention.

FIG. 4 is a cross-sectional view of another optoelectronic semiconductordevice of the inventors of the present invention.

FIG. 5 is a plane-sectional view of another optoelectronic semiconductordevice of the inventors of the present invention.

FIG. 6 shows a part of the optoelectronic semiconductor device accordingto a second example of the present invention.

FIG. 7 shows a part of the optoelectronic semiconductor device accordingto a first modification of the second example of the present invention.

FIG. 8 shows a part of the optoelectronic semiconductor device accordingto a second modification of the second example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings. First, the basic structureand effects of a device according to the present invention will beillustrated and described, and then the materials, sizes,characteristics, detailed structures, etc. will be described in detail.

FIGS. 1 and 2 illustrate an optoelectronic semiconductor device 1according to an embodiment of the present invention. FIG. 1 is asectional view taken vertically. FIG. 2 is a sectional view, taken alongdot-and-dash line AA, of a circuit wiring board 10 in FIG. 1. FIG. 1 isequivalent to a sectional view taken along dot-and-dash line BB in FIG.2. It should also be noted that FIGS. 1 and 2 are shown in scalesdifferent from actual scales for the purpose of easy understanding.

As shown in FIG. 1, the optoelectronic semiconductor device 1 includes asemiconductor photoreceptor or photodetector element 2 which receives alight signal, a semiconductor integrated circuit element 3 electricallyconnected to the semiconductor photoreceptor element 2, and asemiconductor light emitting element 4 electrically connected to thesemiconductor integrated circuit element 3. Elements 2 to 4 are mountedon a circuit wiring board 10. The circuit wiring board 10 is an SLC(Surface Laminar Circuit) board whose base plate is formed of glassepoxy, for example. The circuit wiring board 10 has front and rear sidesopposite to each other, and a plurality of solder ball electrodes 5formed on the front side (lower side in the drawing). The circuit wiringboard 10 also has elements 2 to 4 mounted on the rear side (upper sidein the drawing). As shown in FIGS. 1 and 2, the circuit wiring board 10has electric connection through-holes 6 and light input/outputthrough-holes 7. Each of the electric connection through-holes 6 hasconductive electric wiring layers 6A filled therein, as shown by thehatching in FIG. 1. The solder ball electrodes 5, the semiconductorintegrated circuit element 3, and the optoelectronic semiconductorelements 2 and 4 are electrically connected to each other by theelectric wiring layers 6A filled in the electric connectionthrough-holes 6, wiring lines on the circuit wiring board 10 (not shown)and bump electrodes 9. Also, each of the light input/outputthrough-holes 7 has a light-transparent resin layer 7A filled therein. Amicro lens 8 formed from a light-transparent resin is disposed at thebottom (lower side in the drawing) of each of the light input/outputthrough-holes 7. Each of the semiconductor photoreceptor elements 2receives a light signal from the lower side (in the drawing) through themicro lens 8 and the light-transparent resin layer 7A. Also, thesemiconductor light emitting element 4 transmits a light signal downward(in the drawing) through these elements 8 and 7A.

As shown in FIG. 2, the circuit wiring board 10 of the optoelectronicsemiconductor device 1 in FIG. 1 has sixteen electric connectionthrough-holes 6 formed in the central region thereof and twenty lightinput/output through-holes 7 formed on the periphery thereof. Each ofthe sixteen electric connection through-holes 6 has one solder ballelectrode 5 formed at the bottom thereof. The area of the region wherethe solder ball electrodes 5 are disposed equals less than a quarter ofthe surface area of the circuit wiring board 10. These solder ballelectrodes 5 are formed around a center C of the circuit wiring board10. A maximum of twenty optoelectronic semiconductor elements (2 and 4)are provided for the twenty light input/output through-holes 7. Thecircuit wiring board 10 shown in FIGS. 1 and 2 is 15 mm in width (W), 15mm in depth (L) and 0.37 mm in thickness. In this circuit wiring board10, the electric connection through-holes 6 are 250 μm in diameter andthe light input/output through-holes 7 are 100 μm in diameter.

In the optoelectronic semiconductor device shown in FIGS. 1 and 2, thesemiconductor photoreceptor element 2 receives a first light signal LSINsent from the lower side of the optoelectronic semiconductor device 1(in the drawing) and converts it into a first electronic signal. Thefirst electronic signal is transmitted to the semiconductor integratedcircuit element 3. The semiconductor integrated circuit element 3processes and converts the first electronic signal into a secondelectronic signal, and outputs it from an output terminal. The secondelectronic signal is transmitted to the semiconductor light emittingelement 4 which converts the second electronic signal into a secondlight signal and transmits it downward (in the drawing). In this way,the optoelectronic semiconductor device 1 in FIG. 1 receives the firstlight signal, performs a predetermined processing of the first lightsignal to convert it into the second light signal LSOUT, and transmitsthe second light signal LSOUT.

One of the characteristic features of the optoelectronic semiconductordevice shown in FIG. 1 is that the solder ball electrodes 5 are providedon the front side of the circuit wiring board 10 (lower side in thedrawing), and the optoelectronic semiconductor elements 2 and 4 areprovided on the rear side of the circuit wiring board 10 (upper side inthe drawing). The optoelectronic semiconductor elements transmit andreceive light signals through the light input/output through-holes 7formed on the periphery of the circuit wiring board 10, and the solderball electrodes 5 are disposed in the central region on the rear side ofthe circuit wiring board 10 (lower side in drawing). In this manner, thepresent invention provides an inexpensive, highly reliableoptoelectronic semiconductor device, as will further be described later.

The optoelectronic semiconductor device 1 in FIG. 1 is mounted on anelectro-optical wiring board 31 shown in FIG. 3, and used as a lightsignal input/output device.

FIG. 3 illustrates the light signal input/output device according to theembodiment of the present invention. The light signal input/outputdevice includes the optoelectronic semiconductor device 1 and LSI device35 provided on the electro-optical wiring board 31. In addition, theelectro-optical wiring board 31 includes optical waveguides 32, electricwiring layers 34, 45-degree mirrors 37 and light input/output portions38.

In the light signal input/output device in FIG. 3, the first lightsignal LSIN is sent from the left side (in the drawing) along theoptical waveguide 32. The first light signal LSIN is directed by the45-degree mirror 37 (37A) upward (in the drawing), and is inputted tothe semiconductor photoreceptor element 2 through the light input/outputportion 38 and the light input/output through-hole 7 (light-transparentresin layer 7A) on the left side (in the drawing). The first lightsignal LSIN undergoes predetermined processing operations performed bythe elements 2 to 4, and is re-transmitted as the second light signalLSOUT from the semiconductor light emitting element 4, as mentionedabove. The second light signal LSOUT is resent downward in FIG. 3. Thesecond light signal LSOUT is sent to the optical waveguide 32 againthrough the light input/output through-hole 7 (light-transparent resinlayer 7A) and light input/output portion 38 at the right side (in thedrawing), and then through the 45-degree mirror 37 (37B) at the rightside (in the drawing). Then, the second light signal LSOUT travelsthrough the optical waveguide 32 and in a right-hand direction (in thedrawing). The above-mentioned LSI device 35 is caused to perform apredetermined operation by an electronic signal supplied from theelectric wiring layer 34 via the bump electrode 36.

In the aforementioned optoelectronic semiconductor device 1 shown inFIG. 1 and the light signal input/output device shown in FIG. 3, thesolder ball electrodes 5 are provided on the lower side (in the drawing)of the circuit wiring board 10, and the elements 2 to 4 are provided onthe upper side opposite to the lower side. This makes the structure ofthe circuit wiring board 10 simpler, thereby reducing the manufacturingcost thereof. Furthermore, the elements 2 to 4 cannot be separated fromthe circuit wiring board 10 due to the force of gravity, as in aconventional structure in which the elements are provided on the lowersurface. Accordingly, from the viewpoint of the manufacturing process,the cost of the optoelectronic semiconductor device and the light signalinput/output device can be reduced.

Furthermore, since the optoelectronic semiconductor device 1 in FIG. 1uses the solder ball electrodes 5, the size of the electrodes 5 and theoptoelectronic semiconductor device 1 themselves can be decreased incomparison with the QFP (Quad Flat Package), in which theouter-lead-type electrode terminals are used.

Moreover, in the optoelectronic semiconductor device 1 in FIG. 1 and thelight signal input/output device in FIG. 3, there are provided twentylight input/output through-holes 7. Accordingly, many optoelectronicsemiconductor elements 2 and 4 can be provided. Thus, it is possible tomaintain high performance even with an increased number of lightsignals.

In addition, in the optoelectronic semiconductor device 1 in FIG. 1, thedestruction of the circuit wiring board 10 due to a stress-inducedstrain is prevented, and the separation of solder ball electrodes 5 fromthe circuit wiring board 10 is prevented. This improves the reliabilityof the connection. The optoelectronic semiconductor device 1 willfurther be described below in comparison with another optoelectronicsemiconductor device of the inventors of the present invention (shown inFIGS. 4 and 5).

FIGS. 4 and 5 show a comparative optoelectronic semiconductor device 81.FIG. 4 is a cross-sectional view, corresponding to FIG. 1. FIG. 5 is aplane-sectional view, taken along dot-and-dash line A-A, of a circuitwiring board 90 in the optoelectronic semiconductor device 81 shown inFIG. 4, which corresponds to FIG. 2. The optoelectronic semiconductordevice 81 shown in FIGS. 4 and 5 differs from the optoelectronicsemiconductor device 1 in that light input/output through-holes 87 areformed in the central region of the circuit wiring board 90 andconnecting through-holes 86 (each filled with electric wiring layers86A) and solder ball electrodes 85 are provided on the periphery of thecircuit wiring board 90. The rest of the optoelectronic semiconductordevice 81 is similar to that of the optoelectronic semiconductor device1 according to the embodiment of the present invention (as shown inFIGS. 1 and 2) and will not be described in detail. The circuit wiringboard 90 has a size of 15 mm×15 mm, equal to that of the circuit wiringboard 10 in the embodiment. The optoelectronic semiconductor device 81in FIG. 4 is also mounted on an electro-optical wiring board 31 as shownin FIG. 3. Since the light input/output through-holes 87 (each filledwith a light-transparent resin layer 87A) are formed in the centralregion of the optoelectronic semiconductor device 81 in FIGS. 4 and 5,the optical misalignment with the electro-opticalal wiring board 31 inthe horizontal direction (in the drawing) is advantageously very small.

As described above, the optoelectronic semiconductor device 81 in FIG. 4is to be used on the electro-optical wiring board 31. However, thecircuit wiring board 90 in the optoelectronic semiconductor device 81 isdifferent in coefficient of thermal expansion from the electro-opticalwiring board 31. Therefore, the circuit wiring board 90 of theoptoelectronic semiconductor device 81 is subjected to a strain due tostress caused by a heat cycle. In addition, since the solder ballelectrodes 85 are formed on the periphery of the circuit wiring board 90in the optoelectronic semiconductor device 81 in FIG. 4, a DNP (Distancefrom Neutral Point, namely, a distance from the center C of the circuitwiring board 90) of the solder ball electrodes 85 is large and thecircuit wiring board 90 is somewhat large. This makes a stress-inducedstrain greater. On the assumption that a region in the circuit wiringboard 90 where a stress-induced strain is larger than a mean value is astressed region, a region defined by a dashed line and indicated with areference 91 in FIG. 5 is the stressed area in the optoelectronicsemiconductor device 81 shown in FIGS. 4 and 5. Since the lightinput/output through-holes 87 are provided in this stressed area 91 inthe optoelectronic semiconductor device 81 in FIG. 5, the circuit wiringboard 90 is weaker in the region around the through-holes 87. Therefore,in the optoelectronic semiconductor device 81 shown in FIGS. 4 and 5,the circuit wiring board 90 is disadvantageously easy to break alongbreak lines 92 when a stress-induced strain is caused by the differencein coefficient of thermal expansion between the circuit wiring board 90and the electro-optical wiring board 31.

On the contrary, in the optoelectronic semiconductor device 1 accordingto the embodiment of the present invention, shown in FIG. 1, thestressed area is the region surrounded by the outermost solder ballelectrodes 5. Because of this, the light input/output through-holes 7are formed on the periphery of the stressed area in the optoelectronicsemiconductor device 1 as shown in FIG. 1. As a result, the stressedarea of the circuit wiring board 10 in the semiconductor optoelectronicboard 1 has a greater strength, thereby preventing the circuit wiringboard 10 from being broken. Also, since the DNP (Distance from NeutralPoint) of the solder ball electrodes 5 is small, it is possible to curba stress-induced strain applied to the solder ball electrodes 5, and toprevent the solder ball electrodes 5 from being separated from thecircuit wiring board 10. Thus, the interconnection reliability of theoptoelectronic semiconductor device 1 shown in FIG. 1 can be improved.

However, it has conventionally been considered that in an optoelectronicsemiconductor device and a light signal input/output device, it isdifficult to provide the light input/output through-holes 7 on theperiphery of the circuit wiring board 10 as in the optoelectronicsemiconductor device 1 in FIG. 1. Specifically, it has been consideredthat if the light input/output through-holes 7 were provided on theperiphery of the circuit wiring board 10, thermal expansion andcontraction of the circuit wiring board 10 would cause a large opticalmisalignment, which would in turn result in fluctuations of the opticalcoupling efficiency and hence in a lower connection reliability. Also,the optoelectronic semiconductor device and the light signalinput/output device are required to have the highest optical alignmentaccuracy. The inventors of the present invention know, throughconducting many experiments, that when the collimator lens (micro lens)8 is provided to each of the light input/output through-holes 7 as shownin FIG. 1, the optical coupling efficiency is not decreased very much inthe case of the conventional optoelectronic semiconductor devices andlight signal input/output devices. More specifically, according to theinventors' experiments, when the micro lens 8 was provided, the opticalaxes could be aligned horizontally (in the drawing) with each other withan accuracy of about ±5 to 10 μm at a temperature of −55 to 125° C.Also, the inventors' experiments revealed that the optoelectronicsemiconductor device 1 constructed as shown in FIG. 1 can assure asufficient efficiency of optical coupling and highly reliableinterconnection.

In the light signal input/output device shown in FIG. 3, since thesolder ball electrodes 5 are disposed on the front side of the circuitwiring board 10 of the optoelectronic semiconductor device 1 and theoptoelectronic semiconductor elements 2 and 4 are disposed on the rearside of the circuit wiring board 10, the wiring board 31 and theoptoelectronic semiconductor elements 2 and 4 are somewhat separatedfrom each other. However, the collimator lenses (micro lens) 8 providedin the light signal input/output device in FIG. 3 maintain the opticalcoupling loss between the optoelectronic semiconductor device 1 and theelectro-optical wiring board 31 at about the same level as that in thecase of a conventional light signal input/output device. Thus, it ispossible to maintain a high optical coupling efficiency.

Furthermore, the use of the solder ball electrodes 5 in theoptoelectronic semiconductor device 1 shown in FIG. 1 ensures anaccurate positioning of the optoelectronic semiconductor device 1 andthe electro-optical wiring board 31 in relation to each other in thehorizontal direction (in the drawing) due to the self-alignment effect.This feature also curbs the horizontal optical misalignment, therebyensuring high reliability.

It should be noted, however, that because of the solder ball electrodes5 provided in the optoelectronic semiconductor device 1 shown in FIG. 1,the distance between the electro-optical wiring board 31 and theoptoelectronic semiconductor elements 2 and 4 mounted thereon is likelyto vary. In the optoelectronic semiconductor device 1 shown in FIG. 1,however, it is possible to decrease the variation in the opticalcoupling efficiency by using the collimator lenses 8 even if such avariation in distance occurs, and thus it is possible to maintain highreliability.

Also, in the optoelectronic semiconductor device 1 in FIG. 1 and thelight signal input/output device in FIG. 3, it is possible to improvethe adhesion strength of the collimator lens 8 by forming each of thelight-transparent resin layers 7A, and filling in the light input/outputthrough-holes 7 and the collimator lenses 8 with the same resinmaterial. Therefore, the optoelectronic semiconductor device 1 does notbreak easily even with the collimator lenses 8.

The optoelectronic semiconductor device 1 and the light signalinput/output device are constructed as shown in FIGS. 1 and 3,respectively, as mentioned above. Thus, the present invention canprovide a low-cost, highly reliable optoelectronic semiconductor deviceand light signal input/output device.

In the foregoing descriptions, the optoelectronic semiconductor device 1of FIG. 1 uses the semiconductor photoreceptor element 2 and thesemiconductor light emitting element 4 as the optoelectronicsemiconductor elements. According to the present invention, however,either the semiconductor photoreceptor element 2 or the semiconductorlight emitting element 4 can be used as the need arises.

Also, in the inventors' experiments, the solder ball electrodes 5 areformed in a central portion of the front side of the circuit wiringboard 10 in the optoelectronic semiconductor device 1 in FIG. 1, in anarea smaller than a quarter of the entire front-side surface area of thecircuit wiring board 10. That is, the solder ball electrodes 5 areformed in a limited region. Experiments have proved that thisarrangement could effectively improve the interconnection reliability ofthe solder ball electrodes 5.

EXAMPLE 1

Next, the optoelectronic semiconductor device 1 and the light signalinput/output device will be described in more detail concerning theirmaterials, dimensions, manufacturing methods and characteristics withreference to FIGS. 1 to 3. First, the materials, dimensions andmanufacturing method of the optoelectronic semiconductor device 1 inFIG. 1, and then those of the light signal input/output device in FIG. 3will be described. Finally, the characteristic features of theoptoelectronic semiconductor device 1 and the light signal input/outputdevice will be described.

First, the circuit wiring board 10 of the optoelectronic semiconductordevice 1 in FIG. 1 will be described.

The optoelectronic semiconductor elements 2 and 4 and the semiconductorintegrated circuit 3 are mounted on the circuit wiring board 10. Thecircuit wiring board 10 can be a printed wiring board (SLC) formed byalternately building up insulation layers and conductive layers on aglass epoxy substrate, for example. Also, it is possible to use amultilayer flexible board including a polyimide resin substrate andcopper wires built-up on the surface of the substrate or a build-up typeceramic multilayer board. Among such boards, the SLC board including theglass epoxy substrate as the base plate is used for the circuit wiringboard 10 in this example. The circuit wiring board 10 is a double-sidedcopper-clad glass epoxy substrate 15 mm×15 mm in size, including a 0.37mm-thick glass epoxy resin substrate and an 18 μm-thick copper foillaminated on the substrate. This glass epoxy resin substrate 10 hasthrough-holes 6 of 250 μm in diameter and through-holes 7 of 100 μm indiameter drilled therethrough, as shown in FIG. 1. The through-holes 6and 7 are then subjected to through-hole plating performed withelectroless plating and electroplating. More particularly, thethrough-holes 6 of 250 μm in diameter are formed in the central portionof the glass epoxy resin substrate 10, and the through-holes 7 of 100 μmin diameter are formed on the periphery of the glass epoxy resinsubstrate 10, as shown in FIG. 2. Of these through-holes, each of thethrough-holes 6 of 250 μm in diameter is filled with an electric wiringlayer which provides an electrical connection between the optoelectronicsemiconductor elements 2 and 4 and the semiconductor integrated circuitelement 3 and the solder ball electrodes 5. The through-holes 7 of 100μm in diameter are used as light input/output through-holes forperforming optical coupling of the optoelectronic semiconductor elements2 and 4 with the electro-optical wiring board. Each of the lightinput/output through-holes 7 is filled with a light-transparent resinlayer 43 (as shown in FIG. 6) to prevent the inner walls thereof frombeing electroless-plated.

The circuit wiring board 10 has a copper wiring pattern, an insulatinglayer and a build-up copper wiring layer formed in this order on thecopper-plated through-holes. The circuit wiring board 10 having theaforementioned structure is produced in the following manner, forexample.

First, the substrate having the copper-plated through-holes is coveredwith a resist. Then, a copper wiring pattern is pattern-etched as theresist design by using iron chloride (III). And the copper wiringpattern is designed to have a line/space ratio of 100/100 μm andthrough-hole land diameter of 550 μm, for example.

Next, a photosensitive epoxy resist is applied over the copper wiringpattern formed on the substrate, and then via holes are formed inappropriate positions by exposure and development, thereby forming aninsulation layer of 30 μm in thickness. The via holes are designed tohave a diameter of 75 μm and a land diameter of 150 μm.

Then, a build-up copper wiring layer of 18 μm in thickness is formed onthe insulation layer. The copper-wiring pattern has a line/space ratioof 75/75 μm, for example.

Next, various layers are formed in the same manner as above to form thecircuit wiring board 10 shown in FIG. 1. It should be noted that thewiring layer serving as the uppermost layer is designed to have aline/space ratio of 50/50 μm in consideration of the I/O terminal pitchof the semiconductor integrated circuit element, and that a solderresist of 120 μm in thickness is formed on the front and rear sides ofthe build-up substrate except for the regions of electrodes.

The circuit wiring board 10 in FIG. 1 is thus produced in theaforementioned manner.

Next, the optoelectronic semiconductor device 1 will be describedconcerning the optoelectronic semiconductor elements 2 and 4 and thesemiconductor integrated circuit element 3, mounted on the rear side ofthe circuit wiring board 10, and the solder ball electrodes 5 providedon the front side of the circuit wiring board 10.

According to this example, the semiconductor light emitting element 4 isa vertical cavity surface emitting laser (VCSEL) element which emitslight in a direction perpendicular to the circuit wiring board 10 or avertical cavity surface emitting laser array formed of multiple verticalcavity surface emitting laser elements disposed in an array. Thevertical cavity surface emitting laser element includes GaAs as anactive layer (light-emitting layer). More specifically, an active layer(active region) formed from non-doped GaAs, for example, is formedbetween an n-type GaAlAs clad layer and a p-type GaAlAs clad layer, anda reflecting mirror formed of multiple layers is formed on the outersurface of each of the n-type and p-type GaAlAs clad layers. In thisstructure of the vertical cavity surface emitting laser element, laserlight is emitted in the laminated direction of the clad and activelayers by causing laser oscillation between the two reflecting mirrors.On the surface of the vertical cavity surface emitting laser element 4from which laser light is emitted, there are disposed two types ofelectrodes, i.e., a p-type contact electrode and an n-type contactelectrode. In the vertical cavity surface emitting laser array,eight-by-eight vertical cavity surface emitting laser elements aredisposed on a chip sized 1 mm×1 mm at a pitch of 100 μm, for example.The electrodes are formed from Au/Ni/Ti, for example.

The semiconductor photodetector element 2 is a surface photodetectorelement or a surface photodetector element array formed of a number ofsurface photoreceptor elements disposed in an array. The surfacephotodetector element includes a PIN photodiode serving as aphotoreceptor portion provided on an n⁺-InP substrate, for example. ThePIN photodiode includes a mesa portion and a peripheral portion. Thephotodiode has a laminated structure including an n-InP buffer layer of1.5 μm in thickness (n=10¹⁵ cm⁻³), an n-Ga_(0.47)In_(0.53)As absorptionlayer of 1.9 μm in thickness (n=10¹⁵cm⁻³) and an InP layer of 1.0 μm inthickness (p=10 ¹⁶cm⁻³) laid in this order from the substrate side.

The surface photodetector element 2 and vertical cavity surface emittinglaser element 4 are connected to the circuit wiring board 10 by the bumpelectrodes 9 formed of solder balls of 50 μm in outside diameter and 50μm in height. The optoelectronic semiconductor elements 2 and 4 aredisposed on the light input/output through-holes 7. Because of thisarrangement, a light signal emitted from the vertical cavity surfaceemitting laser element 4, for example, travels through the through-holesserving as light inputs, and are transmitted to the electro-opticalwiring board. It should be noted that although the light signaltransmitted through the through-holes or reflected at the inner walls ofthe through-holes is weaker than during the transmission or reflectionin a light transmitter, such a transmission characteristic causes almostno problem because the length of the transmission distance is severaltens millimeters. Although the material composition of the bumpelectrodes 9 is not limited to any special one so long as the materialis electrically conductive, it should preferably be a metal selectedprimarily from Pb, Sn, Ag, Sb, In and Bi or an alloy containing any ofthem as a main ingredient. According to this example, the material ofthe bump electrodes 9 is Pb/Sn=95/5.

The semiconductor integrated circuit element 3 is electrically connectedto the optoelectronic semiconductor elements 2 and 4, and mounted on thecircuit wiring board 10 with the bump electrodes 9 of an eutectic solderof Pb/Sn=95/5 being laid between the circuit 3 and board 10.

The solder ball electrodes 5 are provided on the front surface (lowerside in the drawing) of the circuit wiring board 10. The solder ballelectrodes 5 should preferably be formed primarily from a metal selectedfrom Pb, Sn, Ag, Sb, In and Bi or an alloy containing any of them as amain ingredient. Also, the melting temperature of the material shouldpreferably be less than that of the metal used to form the bumpelectrodes 9. In this example, the material of the solder ballelectrodes 5 is Pb/Sn=37/63.

The solder ball electrodes 5, the semiconductor integrated circuitelement 3 and the optoelectronic semiconductor elements 2 and 4 aremounted on the aforementioned circuit wiring board 10 to produce theoptoelectronic semiconductor device 1, as will be described below.

First, the flip-chip mounting technique is used to mount thesemiconductor integrated circuit element 3 on the circuit wiring board10 with the bump electrodes 9 being laid between the circuit element 3and the board 10. More specifically, the semiconductor integratedcircuit element 3 having the solder ball electrodes formed thereon isaligned with electrode terminals constituted by circuit wiring lines onthe circuit wiring board 10, using a flip-chip bonder which has a halfmirror and can position the mating elements. It should be noted that thesemiconductor integrated circuit element 3 is held by a collet having aheating mechanism, and pre-heated in a nitrogen atmosphere at 350° C.

Next, the collect is further lowered with the bump electrodes 9 of thesemiconductor integrated circuit element 3 and the electrode terminalsof the circuit wiring board 10 being kept in touch with each other.Namely, a mechanical pressure of 30 kg/mm² is applied to put the bumpelectrodes 9 and the electrode terminals into close contact with eachother. In this condition, the temperature is elevated up to 370° C. tomelt the solder, which connects the electrode terminals of the circuitwiring board 10 to the respective bump electrodes 9 of the semiconductorintegrated circuit 3. It should be noted that a sealing resin can beplaced in a space defined between the semiconductor integrated circuitelement 3 and the circuit wiring board 10 as necessary. It is possibleto use the epoxy resin as the sealing resin, containing a bisphenolepoxy, a imidazole catalyst, acid anhydride as hardener, and sphericalquartz filler in 45 percent by weight, and so on.

Next, the optoelectronic semiconductor elements 2 and 4 are mounted onthe circuit wiring board 10 in the same manner as above with theflip-chip mounting technique. When a sealing resin is used, it ispreferable that a light-transparent resin containing mainlypolymethylmethacrylate (PMMA), deuterated-fluorinated PMMA, fluorinatedpolyimide, silicon, polycyclobutene or the like be used.

Then, the micro lenses (collimator lenses) 8 are provided at the frontends of the light input/output through-holes 7. A micro lens 8 is formedby dripping a small amount of ultraviolet-curable resin liquid onto apredetermined position, and with ultraviolet rays radiating the resindrip, which has been formed to be hemispheric due to the surfacetension, to cure the drip, for example. In consideration of the possiblelight propagation loss, it is preferable that the micro lens 8 be formedfrom the same resin as that filled in the light input/outputthrough-holes 7.

Further, a solder paste is screen-printed on the solder ball electrodeterminals formed on the front side of the circuit wiring board using ascreen-printing metal mask, and then the entire circuit wiring board isreflow-soldered. The solder paste is formed from Pb/Sn=37/63. Thereflow-soldered BGA circuit wiring board is then washed with isopropylalcohol for 10 minutes.

With the above steps of production, the optoelectronic semiconductordevice 1 shown in FIG. 1 is formed.

Next, the light signal input/output device shown in FIG. 3 will befurther described.

The light signal input/output device includes the aforementionedoptoelectronic semiconductor device 1 and LSI devices 35 mounted on theelectro-optical wiring board 31, as shown in FIG. 3. The electro-opticalwiring board 31 may be an OE-MCM board, for example. More specifically,the electro-optical wiring board 31 is composed of an MCM boardincluding a ceramic substrate having circuit wiring lines and build-upwiring lines formed thereon, optical waveguides which serve as opticalwiring layers being formed on the MCM board by etching. Theelectro-optical wiring board may be a flexible board including apolyimide resin substrate serving as a base member and copper wiringlines built up on the surface of the substrate, or a build-up ceramicmultilayer board, for example.

The optoelectronic semiconductor device 1 is mounted on theaforementioned electro-optical wiring board 31 in the following manner.

First, the optoelectronic semiconductor device 1 is roughly aligned withthe electro-optical wiring board 31 using a bonder having a half tonemirror. At this time, a heater on which the optoelectronic semiconductordevice 1 and the electro-optical wiring board 31 are mounted, and acollet holding the optoelectronic semiconductor device 1, have beenheated to 180° C. Since this temperature is lower than the eutectictemperature of the solder forming the solder ball electrodes 5, thesolder ball electrodes 5 are not melted.

Next, the solder ball electrodes 5 of the optoelectronic semiconductordevice 1 are aligned with the electrodes on the electro-optical wiringboard 31. With the solder ball electrodes 5 of the optoelectronicsemiconductor device 1 being thus kept in touch with the electrodes onthe electro-optical wiring board 31, the collet is further lowered toapply a pressure of 30 kg/mm². Then, the solder ball electrodes 5 areput into closer contact with the electrode terminals under themechanical pressure. In this condition, the temperature is elevated upto 250° C. to melt the solder which connects the solder ball electrodes5 of the optoelectronic semiconductor device 1 to the respectiveelectrode terminals of the electro-optical wiring board 31. Thecomposition of each solder ball is Pb/Sn=37/63. Since the composition ofthe bump electrodes 9 used to mount the optoelectronic semiconductorelements 2 and 4 and the semiconductor integrated circuit element 3 withthe flip-chip mounting technique is Pb/Sn=95/5, the bump electrodes 9 ofthe optoelectronic semiconductor device 1 and the semiconductorintegrated circuit element 3 cannot possibly be melted again to cause apoor connection. The connection reliability of the solder ballelectrodes 5 can be improved by placing, only in the central portion ofthe circuit wiring board 10 where the solder balls 5 are disposed butnot including the light input/output through-holes, an epoxy resincontaining, 100 parts by weight of cresol novolak type epoxy resin(ECON-195XL by Sumitomo Chemical Co., Ltd.), 54 parts by weight ofphenol resin serving as hardener, 100 parts by weight of silica servingas filler, 0.5 part by weight of benzildimethylamine serving ascatalyst, 3 parts by weight of carbon black serving as additive and 3parts by weight of silane coupling agent, for example.

The optoelectronic semiconductor device 1 is mounted on theelectro-optical wiring board 31 as having been described above.

The performance of the optoelectronic semiconductor device 1 and thelight signal input/output device, produced as described above, have beenevaluated. The results of the evaluation will be described below.

In the light signal input/output device shown in FIG. 3, the lightinput/output through-holes 7 and the light input/output portions of theelectro-optical wiring board 31 have to be aligned with each other withthe highest level of accuracy. The accuracy of this alignment wasmeasured, and was found to be approximately ±5 μm to 10 μm.

Next, the reliability of the optoelectronic semiconductor device 1 inFIG. 1 was evaluated. The evaluation test was done on an optical modulein which the optoelectronic semiconductor device 1 is mounted on theelectro-optical wiring board 31 as shown in FIG. 3. There were provided64 solder ball electrodes in order to test many wiring lines. Theoptoelectronic semiconductor device 1 was evaluated to be defective whenthe connection of even one of the 64 solder ball electrodes 5 was foundto be disconnected. As comparative samples, there were preparedoptoelectronic semiconductor devices 81 each constructed as shown inFIG. 5 but having a substrate 90 of which the outside dimensions were15.0 mm×15.0 mm, with 64 solder ball electrodes 85. A thousand of thesamples were evaluated with a heat cycle test of −55° C. (for 30 min)˜25° C. (for 5 min) ˜125° C. (for 30 min) ˜25° C. (for 5 min). Theresults of the evaluation showed that a failure connection occurred insome of the optoelectronic semiconductor devices constructed as in FIG.5 after having passed 1,000 heat cycles, and that all the optoelectronicsemiconductor devices incurred a failure connection after having passed2,000 heat cycles. More specifically, the reason of the poor connectionwas that the solder ball electrodes 85 were broken due to astress-induced strain concentrated locally thereon or that the substrate90 was broken due to a stress. In contrast with this, the optoelectronicsemiconductor device 1 constructed as shown in FIG. 2 incurred nofailure connection before having passed 3,500 cycles. Also, the circuitwiring board 10 was not broken even after having passed 3,500 cycles.The results of the evaluation proved that the optoelectronicsemiconductor device 1 constructed as shown in FIG. 1 has an improvedconnection reliability.

The above results of measurement and evaluation have revealed that evenif the optoelectronic semiconductor device 1 shown in FIGS. 1 and 2 ismounted on the electro-optical wiring board 31 which is different incoefficient of thermal expansion from the optoelectronic semiconductordevice 1, the circuit wiring board 10 of the optoelectronicsemiconductor device 1 maintains a high connection reliability withoutany break-down of the circuit wiring board 10.

The first example having been illustrated and described can be modifiedin various manners without departing from the scope and spirit of thepresent invention as defined in the appended claims. The circuit wiringboard used in the first example is an OE-MCM formed of a glass epoxysubstrate, on which an electric wiring layer and an optical wiring layerare stacked. However, the circuit wiring board is not limited theretobut it can be an electro-optical wiring board having optical fibersformed thereon. Also, the optoelectronic semiconductor elements providedin the optoelectronic semiconductor device can include a photodetectorelement and a light emitting element. They may include a semiconductorintegrated circuit element and a CR part, for example. Also, thestructures of the optoelectronic semiconductor elements andsemiconductor integrated circuit element mounted on the circuit wiringboard are not limited to the aforementioned ones. Further, the spacedefined between the optoelectronic semiconductor elements and thecircuit wiring board, the light input/output through-holes, and thelight-transparent resin used to form the micro lenses are not limited tothe aforementioned ones.

EXAMPLE 2

The second example is obtained by modifying the structure around eachlight input/output through-hole 7.

FIG. 6 shows a part of the optoelectronic semiconductor device 1according to the second example of the present invention. FIG. 6corresponds to an expanded view of a left-side portion of theoptoelectronic semiconductor device in FIG. 1. The structure of the mainparts of this portion is the same as that of the first example.Therefore, the structure will not be described in detail.

As shown in FIG. 6, a sealing resin layer 42 of a light-transparentresin is placed in a space between the optoelectronic semiconductorelement 2 or 4 and the circuit wiring board 10. The sealing resin shouldpreferably be a light-transparent resin containing mainlypolymethylmethacrylate (PMMA), deuterated-fluorinated PMMA, fluorinatedpolyimide, silicon, epoxy, polycyclobutene or the like. Also, each ofthe light input/output through-holes 7 is filled with an infilling resinlayer 43 which is formed from a light-transparent resin. The micro lens8 of a light-transparent resin is formed under (in the drawing) eachlight input/output through-hole 7.

The sealing resin layer 42 placed as shown in FIG. 6 can protect theoptoelectronic semiconductor elements 2 and 4, and reduce the lightpropagation loss.

The light propagation loss can be reduced further by forming the sealingresin layer 42, the infilling resin layer 43 and the micro lenses 8 fromthe same resin. More specifically, the optical coupling loss of theoptoelectronic semiconductor elements 2 and 4 can be reduced to about0.2 dB.

Next, modifications of the second example will be described.

FIG. 7 shows a part of a first modification of the optoelectronicsemiconductor device 1 according to the second example. In thismodification, an electrically conductive member 7B, hatched in thedrawing, is provided in a part of each light input/output through-hole 7in order to provide a connection between the wiring lines on the upperside (in the drawing) of the circuit wiring board 10 and the solder ballelectrodes 5. Thus, it is possible to reduce the number of electricalthrough-holes, that is, the number and area of electric connectionthrough-holes 6, which have been the factors limiting a more compactdesign of the circuit wiring board 10, thereby providing ahigher-density circuit wiring board, and achieving a more compactoptoelectronic semiconductor device. More particularly, although thecircuit wiring board 10 in the optoelectronic semiconductor device shownin FIG. 6 has a size of 15.0 mm×15.0 mm, the circuit wiring board shownin FIG. 7 can be 14.0 mm×14.0 mm in size while maintaining the samefunctions as those of the circuit wiring board in FIG. 6.

FIG. 8 shows a part of a second modification of the optoelectronicsemiconductor device 1 according to the second example. The electricallyconductive member 7B, hatched in the drawing, is provided in a part ofeach light input/output through-hole 7, and connected to the bumpelectrodes 9 of the optoelectronic semiconductor element 2 or 4. Inaddition, an electrical wiring layer 45 is provided in a part of thecircuit wiring board 10. In this manner, the optoelectronicsemiconductor device can be decreased in size further. Morespecifically, although the circuit wiring board 10 in the optoelectronicsemiconductor device shown in FIG. 6 has a size of 15.0 mm×15.0 mm, thecircuit wiring board shown in FIG. 8 can be 13.0 mm×13.0 mm in sizewhile maintaining the same functions as those of the circuit wiringboard in FIG. 6.

In each of the aforementioned optoelectronic semiconductor devicesincluding the optoelectronic semiconductor elements to transmit andreceive light signals, the circuit wiring board, and the solder ballelectrodes according to the present invention, the solder ballelectrodes are disposed on the front side of the circuit wiring board,and the optoelectronic semiconductor elements are disposed on the rearside of the circuit wiring board. The optoelectronic semiconductorelements are disposed on the periphery region of the rear side of thecircuit wiring board to transmit and receive light signals through thelight input/output through-holes formed along the periphery of thecircuit wiring board, and the solder ball electrodes are disposed in thecentral region of the front side of the circuit wiring board.Accordingly, it is possible to curb a stress-induced strain caused bythermal expansion of the circuit wiring board applied to the solder ballelectrodes and the circuit wiring board itself. As a result, there canbe provided a optoelectronic semiconductor device lower in cost andhigher in reliability, and a light signal input/output device.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of general inventive conceptas defined by the appended claims and their equivalents.

1. An optoelectronic semiconductor device, mountable on and electricallyconnectable to an electro-optical wiring board, comprising: anoptoelectronic semiconductor element to receive a light signal, transmita light signal or transmit and receive a light signal; a semiconductorintegrated circuit electrically connected to the optoelectronicsemiconductor element; and a circuit wiring board comprising: asubstrate having: first and second sides opposite to each other in thedirection of the thickness, the optoelectronic semiconductor element andthe semiconductor integrated circuit element being mounted on the firstside; a light input/output through-hole, the optoelectronicsemiconductor element inputting/outputting a light signal via the lightinput/output through-hole; and an electric connection through-holes, thesemiconductor integrated circuit element inputting/outputting anelectric signal via wiring layers filled in the electric connectionthrough-holes; and an electrode formed on the second side of thesubstrate, connected to the wiring layers filled in the electricconnection through-holes, and mountable on and electrically connectableto the electro-optical wiring board, the light input/output through-holebeing not formed in a stressed area of the circuit wiring board, butformed in a non-stressed area of the circuit wiring board, the stressedarea being an area where a stress is larger in value than the mean valueof stresses caused in the circuit wiring board by a difference incoefficient of thermal expansion between the circuit wiring board andthe electro-optical wiring board when the electrode on theoptoelectronic semiconductor device is mechanically fixed to andelectrically connected to the electro-optical wiring board.
 2. Thedevice according to claim 1, wherein the semiconductor integratedcircuit is mounted in a central region of the circuit wiring board, andthe optoelectronic semiconductor element is mounted on a peripheralregion of the circuit wiring board.
 3. The device according to claim 2,wherein the electric connection through-hole is formed in the centralregion of the circuit wiring board and the light input/outputthrough-hole is formed on the peripheral region of the circuit wiringboard.
 4. The device according to claim 3, wherein the electricconnection through-hole is formed in the central region whose area is aquarter of the total area of the circuit wiring board, and the lightinput/output through-hole is formed in an area other than the centralregion.
 5. The device according to claim 3, wherein the electrode isprovided in electrical connection with the electric wiring layers filledin the electric connection through-holes.
 6. The device according toclaim 5, wherein the electrode is ball electrodes which fix theoptoelectronic semiconductor device to the electro-optical wiring board.7. The device according to claim 3, wherein the light input/outputthrough-hole is filled with a light-transparent resin that istransparent to the light signal, and a lens is formed on the lightinput/output through-hole at the second side of the circuit wiringboard.
 8. The device according to claim 7, wherein the lens is formedfrom the same material as the light-transparent resin.
 9. The deviceaccording to claim 3, wherein inside the light input/outputthrough-hole, there is provided an electrically conductive memberelectrically connected to the optoelectronic semiconductor element. 10.The device according to claim 9, wherein the electrically conductivemember is electrically connected to an electric wiring layer embedded inthe circuit wiring board.
 11. The device according to claim 3, wherein aspace between the circuit wiring board and the optoelectronicsemiconductor element mounted on the circuit wiring board is sealed by aresin.
 12. The device according to claim 3, wherein a space between thecircuit wiring board and the semiconductor integrated circuit elementmounted on the circuit wiring board is sealed by a resin.
 13. The deviceaccording to claim 3, wherein the optoelectronic semiconductor elementis either a vertical cavity surface emitting laser or a surfacephotodetector element.
 14. The device according to claim 3, wherein: theoptoelectronic semiconductor element includes a light emitting elementand a photoreceptor element, which are provided on the peripheral regionof the circuit wiring board and the semiconductor integrated circuitelement is provided to an internal side of the optoelectronicsemiconductor elements; and correspondingly the light input/outputthrough-holes are formed on the peripheral region of the circuit wiringboard and the electric connection through-holes are formed to aninternal side of the light input/output through-holes.
 15. A lightsignal input/output device comprising: an electro-optical wiring board;and semiconductor devices mounted on the electro-optical wiring device,one of the semiconductor devices being an optoelectronic semiconductordevice which comprises: an optoelectronic semiconductor element toreceive a light signal, transmit a light signal or transmit and receivea light signal; a semiconductor integrated circuit electricallyconnected to the optoelectronic semiconductor element; and a circuitwiring board comprising: a substrate having: first and second sidesopposite to each other in the direction of the thickness, theoptoelectronic semiconductor element and the semiconductor integratedcircuit element being mounted on the first side; a light input/outputthrough-hole, the optoelectronic semiconductor elementinputting/outputting a light signal via the light input/outputthrough-hole; and a electric connection through-holes, the semiconductorintegrated circuit element inputting/outputting a electric signal viawiring layers filled in the electric connection through-holes; and aelectrode formed on the second side of the substrate, connected to thewiring layers filled in the electric connection through-holes, andmountable on and electrically connectable to the electro-optical wiringboard, the light input/output through-holes being not formed in astressed area of the circuit wiring board, but formed in a non-stressedarea of the circuit wiring board, the stressed area being an area wherea stress is larger in value than the mean value of stresses caused inthe circuit wiring board by a difference in coefficient of thermalexpansion between the circuit wiring board and the electro-opticalwiring board when the electrode on the optoelectronic semiconductordevice is mechanically fixed to and electrically connected to theelectro-optical wiring board.
 16. The device according to claim 15,wherein the semiconductor integrated circuit element is mounted in acentral region of the circuit wiring board and the optoelectronicsemiconductor element is mounted on a peripheral region of the circuitwiring board.
 17. The device according to claim 16, wherein the electricconnection through-hole is formed in the central region of the circuitwiring board and the light input/output through-hole is formed on theperipheral region of the circuit wiring board.
 18. The device accordingto claim 17, wherein the electric connection through-holes is formed ina central region whose area is a quarter of the total area of thecircuit wiring board, and the light input/output through-hole is formedin an area other than the central region.
 19. The device according toclaim 17, wherein the electrode is provided in electrical connectionwith the electric wiring layers filled in the electric connectionthrough-holes.
 20. The device according to claim 19, wherein theelectrode is a ball electrode which fix the optoelectronic semiconductordevice to the electro-optical wiring board.